The present invention relates to recording media and recording apparatus thereof.
The use of image signals that have been generated to correspond to an optical image of an object facilitates the performance of edit, trimming and other image processing in the status of electrical signals, and also facilitates the recording and reproduction through the use of a recording material for which the recorded signals can be erased. Conventionally proposed image processing systems in the field of printing and electronic publishing and the like, are as follows: (1) a method where color image signals that have been generated by a color TV camera of the three-tube or single-tube type are recorded to a recording medium such as a VTR, a semiconductor memory, or a magnetic disk or the like, and these are reproduced to obtain color image signals, (2) a method where color image signals that have been generated by a color TV camera of the three-plate or single-plate type are recorded to a recording medium such as a VTR, a semiconductor memory, or a magnetic disk or the like, and these are reproduced to obtain color image signals, and (3) a method where image signals are obtained using a laser telecinema from a color image recorded in a color film by photographing an object by a camera.
In order for the images obtained by image processing systems to be used in the fields of printing and the like, it is required for those images to have a resolution of about 4000 .times. 4000 pixels. Since there is the problem that a higher resolution cannot be obtained with respect to the camera tube or the the solid state image plate, and the recording system, there is a limit to the degree of resolution of about 1000 .times. 2000 pixels obtained by HDTV. More specifically, in the color TV cameras that have been conventionally used to generate image signals, an optical image of an object via a camera lens, is passed through a color splitting system and formed on a photo-electric conversion portion of an image pickup device. Then, in the photo-electric conversion portion, the optical image is converted into electrical image, and that image information is outputted as linear image signals on a time axis. The image pickup devices used in color TV cameras such as this are conventionally various known types of image pickup tubes and solid state image pickup devices.
When the image pickup device for the generation of a image signals for a high-quality and high resolution reproduced image, is an image pickup tube, there is a limit to the degree of fineness of the electron beam diameter in the image pickup tube and so the target capacity of the image pickup tube must be increased so as to correspond to the target area and thus it is not possible to obtain a high resolution. In addition, for example, in case of a color image pickup apparatus for moving picture, there is a problem of the signal-to-noise ratio because the frequency bandwidth of the image signals accompanying high resolution becomes greater than several tens of MHz to several hundreds of MHz. For these reasons, when an image pickup tube is used in a color image pickup apparatus, there are difficulties in generating such image signals that it is possible to reproduce high-quality and high-resolution reproduced images.
In this matter, in a conventional color TC camera, there is a limit to the use of HDTV system for which the image pickup device used as a degree of resolution of 1000 .times. 2000 pixels. Because of this, it is not possible to generate image signals that can reproduce images having a degree of resolution of 4000 .times. 4000 pixels.
In order to eliminate the problem associated with the conventional technology, the applicant of the present invention has proposed a recording and reproduction method using a charge image that can be recorded and reproduced for an image at a high resolution, as disclosed in U.S. Pat. No. 4,831,452, for example. FIG. 1A is a view for describing the principle of the recording method using charge images, described above. In this figure, a recording medium RM is provided with transparent electrodes Et1, Et2, a photoconductive layer member PCL and a photomodulation layer member PML as a recording member. Connected to the recording medium RM are power source Eb and a switch SW.
Instead of the photomodulation layer member PML, a recording member such as a charge holding layer member, a charge image being held therein by a dielectric material can be used, as disclosed in Japanese Patent Laid-Open No. 1990-222924.
In FIG. 1A, after an optical information Pi (an electro-magnetic radiation beam) which is the object of recording focussed by an image pickup lens (not shown), has passed the transparent electrode Et1 and forms an image on the photoconductive layer material PCL, the electrical resistance value of the photoconductive layer material PCL changes in accordance with the optical information. At this time, the switch SW is in the ON status and a voltage Vb that is generated by the power source Eb is impressed across the transparent electrodes Et1 and Et2.
Accordingly, a charge image corresponding to the optical information Pi is formed at the boundary between the photoconductive layer member PCL and the photomodulation layer member PML. This charge image causes an electrical field having a field intensity corresponding to the optical information Pi, to be impressed to the photomodulation layer member PML. As a result, the optical nature of the photomodulation layer member PML changes in accordance with the field intensity. When an electromagnetic radiation beam for reproduction is irradiated to this photomodulation layer member PML via the transparent electrode Et2, the electromagnetic radiation beam for reproduction changes in accordance with the optical nature and is outputted as a reproduced image.
The photomodulation layer material PML described above is conventionally comprised of lead lanthanum titanate, thermoplastic, or a polymer dispersed-liquid crystal film comprising a polymer material having many fine pores that enclose nematic liquid crystal or smectic liquid crystal. When a polymer dispersed crystal film is used as the photomodulation layer member PML, the status of orientation of the crystals in the many fine pores changes so as to correspond to the optical information Pi. As a result, the transmittance of light of the polymer dispersed-liquid crystal film changes in accordance with the optical information Pi.
In the recording medium RM described above, there is shading in a reproduced image obtained by irradiation of an electromagnetic radiation beam for reproduction to the recording medium RM from the transparent electrode Et2 side occurs when the field intensity formed across the transparent electrodes Et1, Et2 by the voltage Vb impressed thereacross from the power source Eb, changes according to portions of the transparent electrodes .An equivalent circuit of the recording medium RM is shown in FIG. 1B. In the circuit shown in FIG. 1B, r11, r12, ... are electrical resistors of the transparent electrode Et1, and r21, r22, r23, ... are electrical resistors of the transparent electrode Et2. The portion shown by an arrow Z in the figure corresponds to the photoconductive layer member PCL and the photomodulation layer member PML.
In the circuit, when the switch SW is ON, a potential difference between portions a and a' of the transparent electrodes Et1 and Et2 is Va-a' = Vb - (r11 + r21) * i1 (i1 is a current flowing through the electrical resistors r11 and r21).
Next, a potential difference between portions b and b' of the transparent electrodes Et1 and Et2 is Vb-b' =Va-a ' - (r12 + r22) * i2 (i2 is a current flowing through the electrical resistors r12 and r22).
Accordingly, Vb &gt; Va-a' &gt; Vb-b', so that the more the portions of the transparent electrodes Et1 and Et2 are apart from connection points P and P' of the power source Eb and the electrodes, the more the potential difference between the electrodes on those portions is decreased as shown in FIG. 1C. The axis of abscissas of FIG. 1C depicts the distance between the connection points P and P' and the portions of the transparent electrodes Et1 and Et2. Shading thus occurs in the output reproduced image as described above.